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Thread: An almost tragic lesson on charge controllers

              
   
   
  1. #1
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    An almost tragic lesson on charge controllers

    Hey all, wanted to share an almost tragic lesson in trusting a crappy voltage cutoff controller from ebay.
    I have a 24 cell chevy volt module on my bike with cell logs on each cell so i can monitor the individual voltages. I plug a ballencer in every month or two and balance the cells when needed.
    The other day I parked my bike in the hot utah sun while charging. I get back and notice that the LCD display is garbled and the LEDs are all lit.
    The unit in question is this one: http://www.ebay.com/itm/DC-Programma...YAAOSwagdXRsqA
    I usually charge to about 98v and have my meanwell supplies set to about 99V. Well turns out the controller died with all outputs on, IE charging my cells and not cutting off at 98V!
    So i didn't really think much about it and get home and plug in the charger and charge all night not knowing the Outputs are stuck on. I get up and find my cell logs yelling at me that 2+ cells are charged to 4.35v!
    I'm not sure how tolerant the LIMN02 cells are to overcharging but I think I'm lucky to not have a fire.

    So.. takeaways for anyone reading this.
    Keep your chargers max voltage low if you have a crappy charge cutoff and if it dies on you, your battery won't overcharge.
    Consider getting a truly industrial rated meter. Even having a balancing circuit may not have helped this as the charging current was much higher than any balancing load could supply.
    Perhaps add redundant cutoff relays. I could have tied the alarm output from the cell logs to the charge circuit.
    Consider extreme heat on the longevity of you control electronics.

    Not sure what else to take away from this, but please add your constructive advice below for others.
    Also anyone think I killed my cells? I have done a few more rides since then and haven't seen any major loss in capacity but still concerned.

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  3. #2
    Senior Member Hugues's Avatar
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    thanks for sharing
    Regards from Switzerland
    My 2.5 Upgrade Thread

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    Administrator ElMotoMike's Avatar
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  5. #4
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    Could you show a schematic of your charging set-up?

  6. #5
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    Charging Circuit.jpg
    This is what I can remember. Basically it is as follows:
    There is an estop on the battery that then connects everything.
    The 12v dc/dc converter powers the avc.2 to handshake with the EVSE via the J1772 port.
    It is always on and never disconnects the EVSE. When the EVSE is connected the chargers both are powered with the output of them in series and the output to the battery gated by a relay.
    That relay is controlled by the charge controller that monitors the pack voltage. If the pack voltage is below the setting then it enables the relay. The charge controller is both powered by the 12v DC/DC converter when the key switch is on and by a 12V power supply then the EVSE is connected. This way the key doesn't need to be present to charge the bike.
    The failure was in the electronics of the charge controller. It overheated in the sun and failed with all outputs high. Which is only a problem when charging and while it was suspect it was not understood that the cutoff would not work until after it was reached. I am not sure if someone makes a simple industrial over voltage cutoff relay but that would have simplified things quite a bit.

  7. #6
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    Thanks for the info. Basic ? Are your switches and relays rated for the DC V and A going through them?

  8. #7
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    yes, other than the estop all switches are actually driving solid state relays with loads well under the rated voltage and current ratings. The estop has a magnetic blowout at 1000A.

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    Was the controller in direct sunlight or in the shade? Unfortunately, I don't see a temp rating for it. I've been through the cobbled together charging set-ups with PSes, and it seems now, in hindsight, it might have been a lot easier just to have gone with an environmentally rated, sealed, dedicated unit. Something like this one: http://www.thunderstruck-ev.com/tsm2...ontroller.html

  10. #9
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    yeah, direct sunlight on a 100F day. That is a nice charge controller! a little pricey though. costs the same as my battery pack did. but less than a burnt down house....
    I looked at some industrial panel meters from legit companies and they are rated for 130F. I bet they also fail gracefully.

  11. #10
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    Do you have examples of the "legit"units?

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